FR2571822A1 - METHOD FOR PROTECTING THE INTERNAL SURFACE OF A CORROSION DRIVING - Google Patents

Abstract

THE PRESENT INVENTION GENERALLY RELATES TO A PROCESS FOR PROTECTING THE INTERIOR SURFACE OF A PIPE AGAINST CORROSION, WHICH CONSISTS OF INSERTING A FLEXIBLE HOSE IN IT, OF MOVING AND APPLYING THIS PIPE ON THE INTERIOR SURFACE OF THE PIPE BY CREATING A EXCESSIVE PRESSURE IN THE ENCLOSURE SHAPED BY THE DUCT, AND THE PIPE, ONE END OF WHICH IS RETURNED INVERY AND FIXED ON THE INSIDE SURFACE OF THE DUCT AND TO HEAT THE SUCH DUCT. ACCORDING TO THE INVENTION, THE HEATING OF THE DUCT IS CARRIED OUT FROM THE INSIDE SIMULTANEOUSLY WITH THE APPLICATION OF THE PIPE ON THE INSIDE SURFACE OF THE DUCT AND WITH THE REGULATION OF THE PRESSURE DIFFERENCE OF TWO SIDES OF THE PIPE INTRODUCED INTO THE DUCT. THE INVENTION FOUND IN PARTICULAR APPLICATION IN WATER SUPPLY FOR HOUSES, INDUSTRIAL ENTERPRISES, AGRICULTURAL SANITATION AND IN THERMAL ENERGY PRODUCTION.

Description

7 1822

  The present invention relates to the construction

  and the exploitation of the pipes and in particular.

  for object the protection of the inner surface

of a pipe against corrosion.

  It is more efficient to use the present invention for the protection of the interior surface of mains and load-bearing or no-load distribution pipe networks used in the water supply of homes, industrial enterprises, sanitation as well as in the production of thermal energy. In addition, the invention can be used in pipes for supplying water to oil and gas production wells as well as for

pumping chemicals.

  The present invention can be used both in the construction of new pipes and in the

  protection of pipes in service.

  At present, protecting the inner surface of pipes has become a major problem. Therefore, it seeks to find as quickly as possible the solution of the problem of protecting the inner surface of the pipes in use because their inner surface is constantly wetted with a liquid, for example water. Before applying a protective coating on the inner surface of the pipe, it must be dried. The drying of this surface must be carried out immediately before the application of a coating because otherwise, the moisture released from the atmospheric air in

  precipitates again on the wall of the pipe.

  Various methods and devices used for the protection of the inner surface are already known.

anti-corrosion pipes.

  Thus, a process is known for applying a cement-sand mixture to the inner surface of the pipes (see the Ameron brochure, edition

  in New York, 1978, pages 548 to 601).

  The disadvantage of this method is that the yield is low because, with the help of this installation, only 690 m of a pipe can be coated per day.

diameter of 700 mm.

  Another method of protecting the inner surface of a pipe against corrosion is known which consists in the introduction into the pipe of a polymer pipe which is applied against

  the previously heated pipe.

  The device implementing this method comprises means for introducing a pipe into a pipe, a system for supplying a driving agent into the pipe and a pipe heater mounted on its surface.

  (see U.S.S.C.

  No. 1018729, Cl. Int. F 16 L 58/00 1982).

  The important disadvantage of this process is that it can not be used for the protection of pipes in service against corrosion. The method described can only be used in the context of factories because in this case, the heater is moved

  following the outer surface of the pipe.

  It was therefore proposed to develop a method of protecting the inner surface of a pipe against corrosion that would ensure effective heating of the inner surface of a pipe already laid in the ground and simplify

  substantially the technology of protection.

  The present invention solves the problem of a method of protecting the inner surface of a pipe against corrosion by inserting therein a flexible pipe, one end of which is turned upside down and secured to the inner surface. the pipe, to move the pipe along the pipe, to apply on the inner surface of the pipe creating, for this purpose, an excess pressure in the cavity formed by the pipe and the pipe and to heat said pipe. The method according to the invention is characterized in that the pipe is heated from the inside, by applying the pipe to the inner surface of the pipe and simultaneously adjusting the difference in pressures on both sides.

  pipe introduced into the pipe.

  According to the present invention, the method makes it possible to create a protective coating on pipes under construction and on those already put into service. This is achievable because the heating of a pipe is from the inside. By simultaneously applying a pipe to a pipe and its heating, it ensures a reliable adhesion of the pipe to the pipe and thus increases the quality of the formed coating which in turn increases the duration

service of a pipe.

  The claimed process provides a protective coating both in pipes under construction and in those already in service and on or on the surface of the ground.

in the ground.

  By regulating the difference of the pressures of the two sides of a pipe to be introduced in the pipe, it is possible to vary the speed of introduction of a pipe, the force of its application to the wall of the pipe, and the risk is eliminated. breaking of the pipe, improving, by

  therefore, the quality of the pipe coating.

  According to a preferred embodiment of the invention, the pipe is heated simultaneously and in synchronism with the introduction of a pipe into the pipe. This improves the coating quality thanks to a constant temperature in the application area

  pipe on the inner surface of a pipe.

  It is advantageous if the difference in pressures is regulated by means of the variation of the driving agent pressure.

  in the pipe in front of the pipe to be inserted.

  This embodiment of the invention makes it possible to

  sea hydraulic and pneumatic shocks in driving

that act on the pipe.

  According to one of the embodiments of the invention, the adjustment of the difference of the pressures in the pipe in front of a pipe to be displaced is done by simultaneously connecting

  the cavity between the pipe and the pipe with the atmosphere.

  This makes it possible to eliminate breaks in the pipe that may occur as a result of an irregular movement thereof. By creating a vacuum in the hollow of the pipe in front of the pipe, the drying conditions of the wall of the pipe are improved and the adhesion of the pipe to the wall of the pipe is improved. It also reduces energy consumption because it reduces the pressure only in a local area

from the hollow of the pipe.

  This helps protect the pipe against breakage

  and improves the quality of the protective coating.

  It is quite advantageous to pose, simultaneously with the introduction of a pipe in the pipe, in the annular spacing between them, protectors made of material capable of creating with the metal of the pipe

an electrochemical potential.

  The device makes it possible to increase the reliability of the pipe because, in addition to the mechanical protection of the pipe, the additional electrochemical protection of the pipe which protects it against

  corrosion in case of: leakage of the pipe.

  According to one of the embodiments of the invention, after the introduction of a polymer pipe, is introduced into this pipe another pipe of non-thermoplastic material. In this case, heating the oonduite will melt

polymer pipe.

  This embodiment makes it possible to create a coating that is fairly strong and resistant to corrosion,

  for example, carboplastic or fiberglass.

  According to the other embodiment of the invention, before introducing a pipe into the pipe, a slip is applied to its inner surface and after the introduction of a glass fabric pipe into the pipe, it is heated. until the merger

of the slip.

  This embodiment of the method makes it possible to increase the strength of the coating and its reliability, which are the characteristics that are particularly important for the protection of a pipe attacked by fluids.

aggressive against corrosion.

  After the slurry melts, pores form in the coating. By creating the pressure in the glass fabric pipe during the heating of the slip, the formation of the pores in the coating is completely suppressed and, consequently,

the reliability of driving.

  It is advantageous that the heating of the pipe of its interior is carried out by pumping a heated gas through the inner pipe of non-combustible material.

thermoplastic.

  This simplifies the drying and heating of the inner surface of the pipe and

to combine these operations.

  In addition, it is advantageous that the heated gas is brought into the pipe to meet the pipe introduced

  and be evacuated through its inner hollow to the atmosphere.

  This embodiment of the invention makes it possible to simplify the drying of the pipe and to adjust the difference in pressures on two sides of the pipe

to introduce.

  According to one of the embodiments of the invention, the heating of the pipe is carried out simultaneously with the introduction of the pipe into it by driving back into said pipe a fuel mixture which is

then inflamed.

  This embodiment makes it possible to create, immediately in the pipe, a high pressure, which substantially simplifies the design of the device

the claimed process.

  The heating of the pipe and its application on the wall of the pipe occur simultaneously. As a result, the quality improves as the pipe fills all the pores and cavities in the pipe wall. The wall of the pipe cools almost at the same time along the entire length of the pipe. As a result, the relaxation stresses in the coating decrease and, consequently, its quality improves. All of this results in a lower cost and higher efficiency of the coating application process, since the displacement of the pipe and its application to the wall of the pipe and its heating are carried out only at the same time. help from a

combustible mixture.

  According to one of the embodiments of the invention, before applying the pipe to the inner surface of a pipe, is brought on said surface

a protective alloy.

  This makes it possible to additionally provide electrochemical protection of the pipe in the event of leakage of the pipe. In addition, the products resulting from the dissolution of the protective alloy form an oxide film which protects several years

driving against corrosion.

  The invention will be better understood and other purposes, = details and advantages of it will appear better at

  the light of the following explanatory description of a

  embodiment given solely by way of non-limiting example, with references to the appended nonlimiting drawing and in which: The method of protecting the inner surface of a pipe against corrosion consists in introducing therein a flexible pipe. Then, turn the front end of the pipe upside down and fix it on the inner surface of the pipe, move it and apply it to the inner surface of the pipe. The displacement and application of the pipe to the pipe is done by means of excess pressure created in the cavity formed by the end turned upside down of the pipe and the pipe. Simultaneously with the application of the pipe to the pipe, the heating of the

the latter from the inside.

Example 1

  A polyethylene pipe is introduced into a pipe. Turn the front end upside down and fix it on the inner surface of the pipe. After that, pressurized compressed air of 0.3 MPa is forced into the cavity formed by the pipe and the pipe. Upstream of the pipe in the hollow of the pipe, is mounted a heater which is moved along the pipe under the action of the pipe performing its movement. It follows

  the hose and heater move simultaneously.

  The inner surface of the pipe is heated up to 150 C. By compressed air, the pipe is clamped against the wall of the pipe and is welded securely to it. During the displacement of the pipe according to the pipe, one creates in front of the pipe the pressure equal to 0,15 MPa. The pressure is created by regulating the supply of compressed air into the hollow of the pipe in front of the pipe. The air is discharged from the pipe to the atmosphere through the orifice formed at the end of the section to be coated in the wall of the pipe. The pressure can be created by drawing air from the pipe in front of the pipe moving in the pipe. Before introducing the pipe into the pipe, it is armed with an aluminum alloy wire. The pipe is heated by bringing a heated gas through the pipe and pipe. The gas can be discharged either from the end of the pipe to meet the displacement of the pipe or first of all following the displacement of the pipe. In both cases, the gas is vented to the atmosphere through the hollow of the pipe.

Example 2

  A polyethylene pipe is engaged inside the

  what is a carboplastic pipe. The front ends of both pipes are turned upside down and secured to the inside surface of the pipe. After that, the air is forced back, heated to a temperature of 150 ° C. under a pressure of 0.2 MPa in the enclosure formed by the pipes. Under the action of air, the pipe moves through the pipe, dries and heats the

  wall of the pipe. The polyethylene pipe melts.

  During the cooling of the polyethylene pipe, the

  inner pipe is welded to the pipe wall.

  It is also possible to return the hot air in the pipe to meet the displaced pipes and

  to vent it to the atmosphere through the inner pipe.

Example 3

  First, we push a slip in the pipe. Then, operating according to the method described in Example 2, two pipes are engaged. The outer pipe is made of polyethylene and the inner pipe is

made of glass fabric.

  After introducing the pipes into the pipe, the inner wall is heated up to the temperature of

500 C.

2 5 7 1 8 2 2

  Under the action of heat, the slip melts

  and weld the two pipes to the pipe wall.

Example 4

  The slip is forced back straight into the pipe. Then, the pipe described in Example 3 is engaged in the pipe. As the driving agent, an oxygen-propane mixture is fed into the pipe in 1/4 weight proportions. After the introduction of the pipes into the pipe, the mixture is ignited. Under the action of heat. released during the combustion of the mixture, the inner wall of the pipe heats up

  and the pipes are soldered to the wall.

Example 5

  By operating in a similar manner to the process described in Example 1, a pipe is

polyethylene in the pipe.

  Prior to engaging the polymer pipe in the pipe, a protective alloy layer is applied to the inner surface by spraying, for example molten aluminum of the following composition in weight percent: 1 magnesium; 0.5 gallium

Rest -aluminium.

  This alloy is heated beforehand to a temperature of 950 C. Then, the molten alloy is pulverized.

  on the wall of the pipe in approximately equal

  80 grams of molten alloy per square meter of surface to be coated. Then, a polyethylene pipe is engaged in the pipe. The fusion of the pipe and the formation of a protective coating are

  under the action of the heated wall of the pipe.

Example 6

  By operating in a similar manner to the process described in Example 1, a polyethylene pipe is engaged in

the driving.

  During the manufacture of the pipe, it is armed with a protective alloy wire, for example, in

  aluminum-gallium alloy indicated in Example 5.

  If the pipe is not sealed, an electrochemical potential is formed between the metal of the pipe

  and wires and protects the pipe from corrosion.

  The wire then dissolves at the damaged part of the pipe and the products of its dissolution are deposited on the wall of the pipe forming an oxide film

  which then protects the pipe against corrosion.

Claims (11)

R E V E N D I C A T IO N S   1. Method of protecting the inner surface   of a corrosion behavior which consists in introducing   drawing a flexible pipe therein, displacing and applying this pipe to the inner surface of the pipe by creating excess pressure in the enclosure formed by the pipe, and the pipe, one end of which is turned upside down and fixed on the inner surface of the pipe and heating said pipe, characterized in that the heating of the pipe is carried out from the inside simultaneously with the application of the pipe on the inner surface of the pipe and with the regulation of the difference pressures on both sides of the pipe introduced into the conduct.   2. Method according to claim 1, characterized in that the heating of the pipe is done simultaneously   and in synchronism with the engagement of the pipe therein.   3. Method according to claim 2, characterized in that the difference in pressure is adjusted by adjusting the pressure of the driving agent in front of the pipe to be introduced into the driving.   4. Method according to claim 1, characterized in that the difference in pressure is adjusted by decreasing the pressure in the pipe upstream of the pipe moving by simultaneously communicating the cavity between   the pipe and the wall of the pipe with the atmosphere.   5. Process according to claims 1 to 4, characterized   in that, simultaneously with the introduction of the pipe into the pipe, in the annular space formed therebetween, protectors made of material capable of   create with the metal of the pipe an electro- chemical.   6. Process according to claims 1 and 2,   characterized in that after introducing into the pipe a polymer pipe, a pipe of non-thermoplastic material and heating is engaged therewith   then the pipe is melted polymer pipe.   7. Process according to claims 1 to 4,   characterized in that before engaging the pipe in the pipe, a slip is applied to its inner surface and after engaging the glass fabric pipe, it is heated until the slurry is melted. 8. Process according to claim 6, characterized in that the pipe is heated by driving back a gas   heated through the inner pipe.   9. A method according to claim 8, characterized in that the heated gas is brought from the end of the pipe in the opposite direction to the displacement of the pipe and discharged through the inner hollow to the atmosphere.   10. Process according to claims 1, 2, 3 and   7, characterized in that it carries out the introduction of the pipe into the pipe and its heating by bringing into   this one a combustible mixture which is then lit.   11. Process according to claims 1 to 10,   characterized in that a protective alloy is applied   before clamping pipe on the surface of the pipe.